Leptin and grehlin: get to know your hunger hormones

In my previous post on metabolic hormones we looked at the role of insulin and glucagon in regulating our blood sugar. This is why diet, weight loss and metabolism is about so much more than just calories in and calories out. These things are dictated by the macronutrients we eat (carbohydrate, protein and fat) and the hormones that are triggered in response to these foods. Now we will have a brief look at two other important players in hormonal hunger regulation: leptin and grehlin.

Leptin

Leptin is often referred to as the ‘fullness’ hormone because it is secreted by your adipose tissue (fat cells) to indicate that you have had enough to eat. It travels to your hypothalamus and tells you to stop eating. It was only discovered in 1994, so there is still a lot more research and learning to be done.

IF and this is a big if, our bodies are working properly then the more fat your have the more leptin you should produce – leading you to eat less. If you are short on fat then you will release less leptin, which means you are hungrier.

Leptin resistance can be a big problem because the body loses the ability to sense that its had enough to eat. You start to need huge amounts of leptin for your body to recognise that it is full, which means you can keep eating and eating without noticing you’ve had enough.

You’d think that they would have found a way to just capture the benefits of leptin and put it in a diet pill to trick your body into thinking it is full. However, studies have shown that leptin injections only work on people that have a genetic deficiency. Most people that are leptin resistant have developed this over time and were not actually born this way. Leptin resistance is classed as a metabolic rather than genetic disorder.

Leptin resistance and insulin resistance are quite similar and often occur together. This means that people with chronically high insulin levels are closer to also becoming leptin resistant. A good place to start when addressing these issues is to reduce your insulin production. You can read about how to do this in my article on insulin.

There is also evidence to suggest that fructose (a form of sugar found in high doses in soft drinks) can have impacts on our leptin production. Frucotse is responsible for a whole suite of metabolic issues, so we will cover it in some more detail in a later post.

Fructose certainly had an impact on leptin production in this study on rats. However, “the mechanism underlying the fructose-induced leptin resistance is not known.” (1) Sugar is half fructose, half glucose and fructose goes straight to the liver without being registered in the rest of the body. Yet another reason to try to avoid or limit your consumption of sugary food and drinks.

When you eat too much carbohydrate and it cannot be stored in the muscles as glucagon, it is stored as fat in two ways: as triglycerides that float in the body or as adipose (fat) tissue. Both of these can decrease leptin sensitivity. High levels of triglycerides in the blood can prevent leptin being transported to the brain.

Other key factors in healthy leptin sensitivity are:

Eating plenty of protein;

Eating soluble fibre (this means starchy vegetables, not grains!);

Getting plenty of good quality sleep;

Reducing stress

Ghrelin

The ‘hungry’ hormone. Ghrelin is a neuropeptide produced by the lining of the stomach and gut to tell your brain you are hungry. It is secreted when the stomach is empty and it then crosses the blood-brain barrier and goes to the hypothalamus to tell you that it’s time to eat. Ghrelin then lowers once you eat and the stomach has been slightly stretched by the food inside.

Interestingly, a lack of sleep can increase ghrelin production, which is why we often feel hungrier after being sleep deprived. Yet another reason for us to prioritise good quality sleep each night.

A final word on food and hormones…

The important message from this brief introduction to leptin and grehlin is to try to eat a balance of all macronutrients and to avoid ending up with any metabolic hormone dysregulation. Many of us living in Western societies where our diets are often grain based do eat too many carbohydrates. This doesn’t mean you must cut them out altogether. A great way to find a good carbohydrate balance is to stick to real food carbs like starches (sweet potato, parsnip, tuba, squash and white potato) and fruit and eat plenty of healthy fats and protein to balance this.